Orthonectidans: Orthonectida

Physical characteristics: Females of Rhopalura ophiocomae (abbreviated as R. ophiocomae) reach a length of 0.01 inch (260 micrometers), males a length of 0.005 inch (130 micrometers). The division of the body is much sharper in males than in females. In females numerous eggs form a compact mass that occupies most of the body. In males the sperm mass is in the middle third of the body.

Geographic range: R. ophiocomae lives off the coasts of France, Great Britain, Italy, and Washington and California in the United States.

Habitat: R. ophiocomae lives in the reproductive and digestive tracts of dwarf brittle stars.

Diet: R. ophiocomae absorbs nutrients in the host's cells.

Behavior and reproduction: R. ophiocomae usually swims with a spiraling motion. To mate, males and females bring their reproductive openings together long enough for the transfer of sperm from the male In Rhopalura ophiocomae, the female's numerous eggs form a compact mass that occupies most of the body. (Specimens in Nouvel collection, Santa Barbara Museum of Natural History, photograph by Hidetaka Furuya. Reproduced by permission.) to the female. Fertilization takes place inside the female. When the embryos are fully developed, the female ruptures and dies, releasing larvae that disperse and enter a new host.

R. ophiocomae and people: R. ophiocomae has no known importance to people.

Conservation status: R. ophiocomae is not threatened or endangered. ∎